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authorWill Deacon <will@kernel.org>2022-12-06 14:01:49 +0300
committerWill Deacon <will@kernel.org>2022-12-06 14:01:49 +0300
commitf6ffa4c8c177c0b52d1c849289b08178f6da0eea (patch)
tree299791f71bfb2a9e9312e59ebcc8d4b157f8b5bc /arch/arm64/include
parent9f930478c648d25e3a4c3db3d69a65cf05ff939a (diff)
parent3b619e22c4601b444ed2d6a5458271f72625ac89 (diff)
downloadlinux-f6ffa4c8c177c0b52d1c849289b08178f6da0eea.tar.xz
Merge branch 'for-next/dynamic-scs' into for-next/core
* for-next/dynamic-scs: arm64: implement dynamic shadow call stack for Clang scs: add support for dynamic shadow call stacks arm64: unwind: add asynchronous unwind tables to kernel and modules
Diffstat (limited to 'arch/arm64/include')
-rw-r--r--arch/arm64/include/asm/module.lds.h8
-rw-r--r--arch/arm64/include/asm/scs.h49
2 files changed, 57 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
index 094701ec5500..dbba4b7559aa 100644
--- a/arch/arm64/include/asm/module.lds.h
+++ b/arch/arm64/include/asm/module.lds.h
@@ -17,4 +17,12 @@ SECTIONS {
*/
.text.hot : { *(.text.hot) }
#endif
+
+#ifdef CONFIG_UNWIND_TABLES
+ /*
+ * Currently, we only use unwind info at module load time, so we can
+ * put it into the .init allocation.
+ */
+ .init.eh_frame : { *(.eh_frame) }
+#endif
}
diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h
index 8297bccf0784..ff7da1268a52 100644
--- a/arch/arm64/include/asm/scs.h
+++ b/arch/arm64/include/asm/scs.h
@@ -5,6 +5,7 @@
#ifdef __ASSEMBLY__
#include <asm/asm-offsets.h>
+#include <asm/sysreg.h>
#ifdef CONFIG_SHADOW_CALL_STACK
scs_sp .req x18
@@ -24,6 +25,54 @@
.endm
#endif /* CONFIG_SHADOW_CALL_STACK */
+
+#else
+
+#include <linux/scs.h>
+#include <asm/cpufeature.h>
+
+#ifdef CONFIG_UNWIND_PATCH_PAC_INTO_SCS
+static inline bool should_patch_pac_into_scs(void)
+{
+ u64 reg;
+
+ /*
+ * We only enable the shadow call stack dynamically if we are running
+ * on a system that does not implement PAC or BTI. PAC and SCS provide
+ * roughly the same level of protection, and BTI relies on the PACIASP
+ * instructions serving as landing pads, preventing us from patching
+ * those instructions into something else.
+ */
+ reg = read_sysreg_s(SYS_ID_AA64ISAR1_EL1);
+ if (SYS_FIELD_GET(ID_AA64ISAR1_EL1, APA, reg) |
+ SYS_FIELD_GET(ID_AA64ISAR1_EL1, API, reg))
+ return false;
+
+ reg = read_sysreg_s(SYS_ID_AA64ISAR2_EL1);
+ if (SYS_FIELD_GET(ID_AA64ISAR2_EL1, APA3, reg))
+ return false;
+
+ if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) {
+ reg = read_sysreg_s(SYS_ID_AA64PFR1_EL1);
+ if (reg & (0xf << ID_AA64PFR1_EL1_BT_SHIFT))
+ return false;
+ }
+ return true;
+}
+
+static inline void dynamic_scs_init(void)
+{
+ if (should_patch_pac_into_scs()) {
+ pr_info("Enabling dynamic shadow call stack\n");
+ static_branch_enable(&dynamic_scs_enabled);
+ }
+}
+#else
+static inline void dynamic_scs_init(void) {}
+#endif
+
+int scs_patch(const u8 eh_frame[], int size);
+
#endif /* __ASSEMBLY __ */
#endif /* _ASM_SCS_H */